This invention relates to a ventilator and an improved ventilating method.
It is common for patients in the intensive care unit to be connected to mechanical ventilators to provide partial or complete assistance in breathing.
Weaning patients from ventilatory support is one of the major challenges involved in their case. The weaning process involves the application of an appropriate level of partial ventilatory support coupled with an ongoing assessment of the patient's status, so that the support level may be adjusted as necessary. For effective implementation this process requires that the mechanical properties of the patient's respiratory system be monitored regularly. With this information the magnitude of the muscular breathing efforts applied by the patient can be determined, and any adverse changes in the mechanical properties of the lungs can be determined.
The mechanical properties of the lungs are crucial determinants of their ability to function properly. Despite this, the assessment of respiratory mechanical function in mechanically ventilated patients in the intensive care unit is currently rudimentary, being limited for the most part to consideration of peak airway pressures and to visual inspection of flow-volume loops.
Many mechanical ventilators are available commercially. However, none is able to deliver both conventional ventilation flow waveforms and high frequency ventilation simultaneously. Also, although most modern ventilators have a variety of available flow waveforms they can deliver during inspiration, these are all pre-programmed and represent those considered the most important at the time of manufacture. No commercially available ventilator can deliver an arbitrary inspiratory flow waveform (within its band-width capabilities) with high precision.
Although some ventilators have the capability to estimate simple parameters of patient respiratory mechanics, there is a need for greater accuracy of signal measurement and greater sophistication in the analysis methods used.